1. Field of the Invention
The present invention relates to an organic light emitting compound and an organic light emitting device including the same, and more particularly, to an organic light emitting compound having excellent electric properties, thermal stability, and photochemical stability such that an organic light emitting device using the organic light emitting compound has low operating voltage and color purity and an organic light emitting device including an organic layer formed of the organic light emitting compound.
2. Description of the Related Art
Light-emitting devices are devices that generate and emit light and have wide angles of light emission, excellent contrast, and short response times. Light emitting devices can be categorized into inorganic light emitting devices having light emitting layers formed of inorganic compounds and organic light emitting devices (OLEDs) having light emitting layers formed of organic compounds. OLEDs have high brightness, low operating voltages, and short response times, and can realize emission of a large range of colors of light, when compared to inorganic light emitting devices. As a result, a lot of research into OLEDs has been conducted.
In general, an OLED has a layered structure of anode/organic light emitting layer/cathode. In addition, an OLED can have various layered structures such as a structure of anode/hole injection layer/hole transport layer/light emitting layer/electron transport layer/electron injection layer/cathode or a structure of anode/hole injection layer/hole transport layer/light emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode.
Materials used to manufacture OLEDs can be categorized into vacuum deposition materials and solution coating materials according to a method of preparing a corresponding organic layer. A vacuum deposition material should have a vapor pressure of 10−6 torr or higher at 500° C. or less and may be a small molecular material having a molecular weight of 1200 or less. A solution coating material should have high solubility with respect to a solvent such that it can be prepared in a liquid state and should include an aromatic family or heterocyclic materials.
When an OLED is manufactured using a vacuum deposition method, a vacuum system is required and thus manufacturing costs are increased, and when a shadow mask is used to define a pixel used for displaying natural color, it is difficult to obtain a pixel having high resolution. On the other hand, a solution coating method, such as an inkjet printing method, a screen printing method, or a spin coating method, can be easily used, is inexpensive, and can be used to obtain a relatively higher pixel resolution than when a shadow mask is used.
However, among materials that can be used in a solution coating method, blue light emitting molecules exhibit inferior thermal stability and color purity compared to materials that can be used in a vacuum deposition method. In addition, even when blue light emitting molecules have high thermal stability and high color purity, an organic layer formed of the blue light-emitting molecules is gradually crystallized such that the size of the formed crystals corresponds to a wavelength of visible light. As a result, visible rays are dispersed, a whitening effect takes place, and pinholes may be formed. Thus the corresponding device may easily deteriorate.
In Japanese Patent Laid-open Publication No. 1999-003782, anthracene substituted for 2 Naphthyl groups is disclosed as a compound which can be used in an light emitting layer or a hole injection layer. However, a solvent solubility of anthracene is insufficient and an organic light emitting device including such compound exhibits inferior performance.
Accordingly, improvements are required to develop an organic light emitting device having low operating voltage, high brightness, high efficiency, and high color purity using a blue light emitting compound which has good thermal stability and can be used to form an organic layer with good quality.